Platen planarizing process for additive manufacturing system

ABSTRACT

A method for printing a three-dimensional part with an additive manufacturing system, the method comprising generating and printing a planarizing part having a substantially-planar top surface relative to a build plane, and a bottom surface that substantially mirrors a topography of a platen surface, and printing the three-dimensional part over the substantially-planar top surface of the printed planarizing part.

BACKGROUND

The present disclosure relates to additive manufacturing systems forprinting three-dimensional (3D) parts and support structures. Inparticular, the present disclosure relates to processes for planarizingplatens used in additive manufacturing systems.

Additive manufacturing systems are used to print or otherwise build 3Dparts from digital representations of the 3D parts (e.g., AMF and STLformat files) using one or more additive manufacturing techniques.Examples of commercially available additive manufacturing techniquesinclude extrusion-based techniques, jetting, selective laser sintering,powder/binder jetting, electron-beam melting, and stereolithographicprocesses. For each of these techniques, the digital representation ofthe 3D part is initially sliced into multiple horizontal layers. Foreach sliced layer, a tool path is then generated, which providesinstructions for the particular additive manufacturing system to printthe given layer.

For example, in an extrusion-based additive manufacturing system, a 3Dpart may be printed from a digital representation of the 3D part in alayer-by-layer manner by extruding a flowable part material. The partmaterial is extruded through an extrusion tip carried by a print head ofthe system, and is deposited as a sequence of roads on a platen in anx-y plane. The extruded part material fuses to previously deposited partmaterial, and solidifies upon a drop in temperature. The position of theprint head relative to the substrate is then incremented along a z-axis(perpendicular to the x-y plane), and the process is then repeated toform a 3D part resembling the digital representation.

In fabricating 3D parts by depositing layers of a part material,supporting layers or structures are typically built underneathoverhanging portions or in cavities of 3D parts under construction,which are not supported by the part material itself. A support structuremay be built utilizing the same deposition techniques by which the partmaterial is deposited. The host computer generates additional geometryacting as a support structure for the overhanging or free-space segmentsof the 3D part being formed. Support material is then deposited from asecond nozzle pursuant to the generated geometry during the printingprocess. The support material adheres to the part material duringfabrication, and is removable from the completed 3D part when theprinting process is complete.

SUMMARY

An aspect of the present disclosure is directed to a method for printinga 3D part with an additive manufacturing system having a platen with aplaten surface. The method includes measuring heights of multiple pointsof the platen surface, which provide a mapped topography of the platensurface, calculating a height of a planarizing part as a function of themeasured heights, and generating a digital model of the planarizing partbased on the calculated height and the mapped topography of the platensurface. The method also includes printing the planarizing part with theadditive manufacturing system based on the generated digital model ofthe planarizing part, where the printed planarizing part has asubstantially-planar top surface in a build plane, and a bottom surfacethat substantially mirrors the mapped topography of the platen surface.The method further includes printing the 3D part over thesubstantially-planar top surface of the printed planarizing part.

Another aspect of the present disclosure is directed to a method forprinting a 3D part, which includes measuring heights of multiple pointsof a platen surface of a platen retained by an additive manufacturingsystem, which provide a mapped topography of the platen surface. Themethod also includes determining a peak height based on the measuredheights, and calculating a height of a planarizing part as a function ofthe determined peak height and a slice thickness for the planarizingpart. The method further includes generating a digital model of theplanarizing part having a substantially-planar top surface at thecalculated height, and a bottom surface that mirrors the mappedtopography of the platen surface. The method further includes printingthe planarizing part with the additive manufacturing system based on thegenerated digital model of the planarizing part. In some embodiments,the method further includes printing at least one of the 3D part and asupport structure for the 3D part onto the printed planarizing part.

Another aspect of the present disclosure is directed to an objectprinted with an additive manufacturing system having a platen with aplaten surface. The object includes a 3D part, optionally, a supportstructure for the three-dimensional part, wherein the 3D part and theoptional support structure have a bounding box in a build plane, and aplanarizing part. The planarizing part includes a top surface on whichone or both of the 3D part and the optional support structure areprinted, where the top surface is substantially planar in the buildplane. The planarizing part also includes a bottom surface thatsubstantially mirrors a topography of the platen surface on which theplanarizing part is printed, and a cross-section in the build planedefined at least in part by the bounding box.

Definitions

Unless otherwise specified, the following terms as used herein have themeanings provided below:

The terms “preferred” and “preferably” refer to embodiments of theinvention that may afford certain benefits, under certain circumstances.However, other embodiments may also be preferred, under the same orother circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the present disclosure.

Directional orientations such as “above”, “below”, “top”, “bottom”, andthe like are made with reference to a layer-printing direction of a 3Dpart. In the embodiments shown below, the layer-printing direction isthe upward direction along the vertical z-axis. In these embodiments,the terms “above”, “below”, “top”, “bottom”, and the like are based onthe vertical z-axis. However, in embodiments in which the layers of 3Dparts are printed along a different axis, such as along a horizontalx-axis or y-axis, the terms “above”, “below”, “top”, “bottom”, and thelike are relative to the given axis.

The term “build plane” refers to a plane in which the layers of a 3Dpart are oriented, and is perpendicular to the layer-printing directionof the 3D part.

The term “height”, such as with reference to a height of a platensurface, is taken along the layer-printing direction of the 3D part, andis perpendicular to the build plane.

The term “bounding box” refers to a cross-sectional area footprint inthe build plane in which the 3D part(s) and any optional supportstructure(s) are to be printed.

Unless otherwise specified, temperatures referred to herein are based onatmospheric pressure (i.e. one atmosphere).

The term “providing”, such as for “providing a consumable material”,when recited in the claims, is not intended to require any particulardelivery or receipt of the provided item. Rather, the term “providing”is merely used to recite items that will be referred to in subsequentelements of the claim(s), for purposes of clarity and ease ofreadability.

The terms “about” and “substantially” are used herein with respect tomeasurable values and ranges due to expected variations known to thoseskilled in the art (e.g., limitations and variabilities inmeasurements).

The term “substantially planar in a build plane”, with reference to atop surface of a planarizing part (or digital model thereof), includesdeviations from exact flatness due to variations in the movementtrajectories of a print head, a calibration device, or the like. This isexplained further below with reference to head gantry bowing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an additive manufacturing system configured toprint 3D parts with a planarizing part of the present disclosure.

FIG. 2 is a perspective view of a platen of the additive manufacturingsystem, illustrating an example bounding box.

FIGS. 3A-3C are exaggerated illustrations of planarity deviations of asurface of the platen relative to a build plane.

FIGS. 4A-4C are exaggerated illustrations corresponding to the views ofFIGS. 3A-3C, with a printed planarizing part having substantially planartop surface, and a bottom surface that substantially mirrors theplanarity deviations of the platen surface.

FIG. 5 is a flow diagram of a method for printing a 3D part using aplanarizing process of the present disclosure.

FIG. 6 is a perspective view of the platen, illustrating a planarizingpart printed in the bounding box.

FIG. 7 is a view of the platen, illustrating the planarizing part, asupport structure, and a 3D part printed in the bounding box.

DETAILED DESCRIPTION

The present disclosure is directed to a process for planarizing a platenused in an additive manufacturing system. Additive manufacturing systemsare preferably capable of printing 3D parts with high resolutions, suchas with good part details, thin layers, and the like. To produce thehigh resolutions, the printed layers are preferably deposited ontoplanar surfaces to reduce layer-height variations, and to ensure goodadhesive bonds to the underlying platen surfaces. As such, theunderlying platens that receive the printed layers of the 3D parts arepreferably planar in the build plane (i.e., flat and level relative tothe print head movement trajectory), where deviations from thisplanarity can potentially reduce layer accuracies, as well as reducingadhesive bonding, which can potentially affect depositional accuraciesand layer curling.

For example, large platens (e.g., 6-feet×8-feet) used in some additivemanufacturing systems are typically required to be rigid and heavy tohold flatness to within a single layer thickness. As can be appreciated,manufacturing large platens within these flatness tolerances can bedifficult and expensive. As such, the platen surfaces may exhibit smallhills and valleys due to manufacturing limitations. Moreover, theplatens may not necessarily be level with the intended build planes whenmounted to platen gantries of the additive manufacturing systems. Assuch, the platen surfaces may also exhibit non-level sloping relative tothe build planes.

One current technique for improving platen planarity in the build planeinvolves measuring the platen surface at multiple points, determining anapproximate best height for the first printed layer, and thenover-depositing the first layer, which deposits excess amounts of thematerial (i.e., thick deposited roads). This partially reduces theeffects of surface non-planarity, and can increase the amount ofdeposited material that adheres to the platen surface. However, thistechnique is typically limited to smaller flatness and levelnessdeviations (e.g., small hills and valleys in the platen surface), whichcan still be difficult and expensive to achieve.

Instead, the planarizing process of the present disclosure may furtherimprove surface planarity in the build plane, particularly whenutilizing large platens. Briefly, the planarizing process involvesmeasuring the height of the platen surface at multiple points toidentify deviations from surface flatness and levelness relative to thebuild plane. This effectively maps the topography of the platen surface,and is preferably limited to a bounding box in which the 3D parts andsupport structures are to be printed (to reduce time and materialrequirements).

The mapped topography of the platen surface is typically limited to thearea of the platen surface in which the multiple points are measured. Assuch, as used herein, the expression “mapped topography of the platensurface”, and similar variations thereof, refer to the topography of theplaten surface in which the multiple points are measured. Accordingly,the mapped topography may include an entire surface area of the platensurface if the entire platen surface is measured, or may include onlyone or more subregions thereof if the measurements are made only inthese subregion(s).

From there, a planarizing part may be generated and printed, whichcompensates for the deviations from surface flatness and levelnessrelative to the build plane. In particular, the printed planarizing partpreferably has a bottom surface that is a substantial mirror image oftopography of the measured platen surface, and a top surface that issubstantially planar in the build plane (i.e., substantially flat andlevel relative to the print head movement trajectory). This ensures thatthe printed material achieves good adhesive bonding to the platensurface.

The additive manufacturing system may then print one or more 3D partsand/or support structures on top of the printed planarizing part. Thesubstantially-planar top surface of the planarizing part accordinglyallows subsequent 3D parts and support structures to be printed withhigh resolutions, while also allowing the platen to be manufactured andinstalled with reasonable tolerances.

FIG. 1 illustrates system 10, which is an example additive manufacturingsystem for printing or otherwise building 3D parts and supportstructures using a layer-based, additive manufacturing technique, andutilizing the planarizing process of the present disclosure. Suitableadditive manufacturing systems for system 10 include extrusion-basedadditive manufacturing systems developed by Stratasys, Inc., EdenPrairie, Minn. under the trademarks “FDM” and “FUSED DEPOSITIONMODELING”. Alternatively, system 10 may be any suitable additivemanufacturing system that incorporates a platen (i.e., build substrate),and is particularly suitable for use with deposition-based additivemanufacturing systems, such as extrusion-based and jetting-basedsystems.

In the shown example, system 10 includes chamber 12, platen 14, platengantry 16, print head 18, head gantry 20, and consumable assemblies 22and 24. Chamber 12 is an enclosed environment that contains platen 14for printing 3D parts and support structures. Chamber 12 may be heated(e.g., with circulating heated air) to reduce the rate at which the partand support materials solidify after being extruded and deposited (e.g.,to reduce distortions and curling). In alternative embodiments, chamber12 may be omitted and/or replaced with different types of buildenvironments. For example, a 3D part and support structure may beprinted in a build environment that is open to ambient conditions or maybe enclosed with alternative structures (e.g., flexible curtains).

Platen 14 is a platform having platen surface 14 a on which 3D parts andsupport structures are printed in a layer-by-layer manner, and issupported by platen gantry 16. As discussed above, manufacturing aplaten surface 14 a with high levels of flatness can be difficult andexpensive, particular in embodiments in which platen 14 has a largesurface in the build plane. Moreover, when installed to platen gantry16, platen surface 14 a may not necessarily level relative to the buildplane, potentially resulting in non-level sloping.

In some embodiments, platen surface 14 a may also include a removablesubstrate such as a flexible polymeric film or liner on which the 3Dparts and support structures are printed, an adhesive tape, a painted-onlayer of adhesive, a cardboard liner, or a build tray such as isdisclosed in U.S. patent application Ser. No. 13/791,005. As such, theterm “platen surface” refers to the surface upon which the planarizingpart is printed, which may be the actual surface of platen 14 and/or afilm, liner, or other substrate disposed on the actual surface of theplaten. Platen gantry 16 is a gantry assembly configured to move platen14 along (or substantially along) the vertical z-axis. Correspondingly,print head 18 is supported by head gantry 20, which is a gantry assemblyconfigured to move print head 18 in (or substantially in) the horizontalx-y plane above chamber 12.

In the shown example, print head 18 is a dual-tip extrusion headconfigured to receive consumable filaments from consumable assemblies 22and 24 (e.g., via guide tubes 26 and 28) for printing 3D part 30 andsupport structure 32 on platen surface 14 a. Examples of suitabledevices for print head 18, and the connections between print head 18 andhead gantry 20 include those disclosed in Crump et al., U.S. Pat. No.5,503,785; Swanson et al., U.S. Pat. No. 6,004,124; LaBossiere, et al.,U.S. Pat. Nos. 7,384,255 and 7,604,470; Leavitt, U.S. Pat. No.7,625,200; Batchelder et al., U.S. Pat. No. 7,896,209; and Comb et al.,U.S. Pat. No. 8,153,182. In additional embodiments, in which print head18 is an interchangeable, single-nozzle print head, examples of suitabledevices for each print head 18, and the connections between print head18 and head gantry 20 include those disclosed in Swanson et al., U.S.Pat. No. 8,419,996. In jetting-based systems, print head 18 may be aninkjet head such as described in Kritchman et al., U.S. Pat. No.8,323,017.

Consumable assembly 22 may contain a supply of a part material forprinting 3D part 30, and consumable assembly 24 may contain a supply ofa support material for printing support structure 32 from the givensupport material. As further shown in FIG. 1, print head 18 may alsoprint planarizing part 34 from the part or support materials pursuant tothe planarizing process of the present disclosure, as discussed below.Collectively, 3D part 30, support structure 32, and planarizing part 34may be referred to as printed object 35, where support structure 32 maybe optionally included when needed (e.g., to support 3D part 30).

In an alternative embodiment, platen 14 may be configured to move in thehorizontal x-y plane within chamber 12, and print head 18 may beconfigured to move along the z-axis. Other similar arrangements may alsobe used such that one or both of platen 14 and print head 18 aremoveable relative to each other. Platen 14 and print head 18 may also beoriented along different axes. For example, platen 14 may be orientedvertically and print head 18 may print 3D part 30 and support structure32 along the x-axis or the y-axis.

System 10 also includes controller 36, which is one or more controlcircuits configured to monitor and operate the components of system 10.For example, one or more of the control functions performed bycontroller 36 can be implemented in hardware, software, firmware, andthe like, or a combination thereof. Controller 36 may communicate overcommunication line 38 with chamber 12 (e.g., with a heating unit and/orair blower for chamber 12), platen gantry 16, print head 18, head gantry20, and/or various sensors, calibration devices, display devices, and/oruser input devices.

While illustrated as a single signal line, communication line 38 mayinclude one or more electrical, optical, and/or wireless signal lines,allowing controller 36 to communicate with various components of system10. Furthermore, while illustrated outside of system 10, controller 36and communication line 38 may be internal components to system 10.

System 10 and/or controller 36 may also communicate with one or morecomputer-based systems, referred to as computer 40, which may includecomputer-based hardware, such as data storage devices, processors,memory modules and the like for generating, storing, and transmittingtool path and related printing instructions to system 10. Accordingly,computer 40 may also be external and/or internal to system 10. Forexample, computer 40 may be one or more external computer systems (e.g.,desktop, laptop, server-based, cloud-based, tablet, mobile media device,and the like) configured to communicate with system 10 and/or controller36 over one or more wired and/or wireless communication lines, referredto as communication line 42. Alternatively, computer 10 may be internalto system 10, and may communicate with one or more external computerdevices.

In some embodiments, controller 36 itself may perform one or more of theoperations typically performed by computer 40 or other components ofsystem 10, such as generating and storing tool path and related printinginstructions, perform compiler functions, and the like. In furtherembodiments, controller 36 and computer 40 may be integrated into acommon device that performs the operations of both controller 36 andcomputer 40. Furthermore, in some embodiments, the steps of theplanarizing process of the present disclosure may be performed in aback-and-forth manner, where controller 36 and computer 40 transmit databetween each other to in an iterative manner to perform the steps of theplanarizing process.

Accordingly, controller 36 and computer 40 may be collectively referredto as controller system 44. It is understood that computer-basedcalculations, data recording, data generation, data storage, and thelike may be performed with the computer-based hardware and software ofcontroller system 44 (i.e., controller 36 and/or computer 40), such aswith one or more processors and computer storage media of controllersystem 44, as is well known to those skilled in the art.

During a printing operation, controller system 44 may direct platengantry 16 to move platen 14 to a predetermined height within chamber 12.Controller system 44 may then direct head gantry 20 to move print head18 around in the horizontal x-y plane above chamber 12. Controllersystem 44 may also direct print head 18 to selectively draw successivesegments of the consumable filaments from container portions 22 and 24,and through guide tubes 26 and 28, respectively. This thermally meltsthe received successive segments such that the consumable filamentsbecome molten materials. The molten materials are then selectivelyextruded from print head 18 and deposited onto platen 14 for printingplanarizing part 34, and then 3D part 30 and support structure 32, in alayer-by-layer manner.

As can be appreciated, when platen surface 14 a has even smalldeviations from planarity in the build plane, this can adversely affectprinting accuracies, as well as affecting the adhesive bonding of thedeposited materials to platen surface 14 a. For example, as shown inFIG. 2, platen 14 may be mounted to platen gantry 16 (shown in FIG. 1)such that platen surface 14 a is oriented in the x-y build plane as muchas reasonably possible. However, due to manufacturing limitations,platen surface 14 a may exhibit small hills and valleys that aredeviations above and below an average height of platen surface 14 a(i.e., non-flatness). Additionally, platen surface 14 a may also deviatefrom levelness relative to the x-y build plane. This can create asloping effect having a hill portion extending above the average heightof platen surface 14 a, and a valley portion extending below the averageheight of platen surface 14 a.

As mentioned above, the relevant hills and valleys are preferablylimited to a bounding box or footprint in which the 3D parts and supportstructures are to be printed, such as bounding box 46 shown in FIG. 2.This may reduce the time required to measure platen surface 14 a, aswell as reducing time and material requirements during the printingoperation. However, in alternative embodiments, the hills and valleysmay encompass the entirety of platen surface 14 a, if desired or needed.

FIG. 3A is an exaggerated illustration of example hills and valleys ofplaten surface 14 a relative to the x-y build plane, which are referredto as hill 48 and valley 50, and which are preferably located withinbounding box 46. As can been seen, hill 48 and valley 50 are respectivedeviations above and below an average height of platen surface 14 a(referred to as average surface height 52), which is also preferablymeasured within bounding box 46. In the shown example, hill 48 has aheight 48 h, which deviates above average surface height 52 by heightdeviation 48 d. Similarly, valley 50 has a height 50 h, which deviatesbelow the average surface height 52 by height deviation 50 d.

Alternatively, as shown in FIG. 3B, platen surface 14 a may exhibit anon-level slope relative to the x-y build plane. This non-level slope ofplaten surface 14 a may, for example, be due to small misalignments ofplaten gantry 16 and/or installation limitations when mounting platen 14to platen gantry 16. This slope accordingly creates a hill 48 havingheight 48 h that deviates above average surface height 52 by heightdeviation 48 d, and a valley 50 having height 50 h that deviates belowaverage surface height 52 by height deviation 50 d.

Within bounding box 46, and due to the sloped nature of platen surface14 a, hill 48 typically has a height deviation 48 d above the averagesurface height 52 at a boundary of bounding box 46. Similarly, valley 50typically has a height deviation 50 d below the average surface height52 at an opposing boundary of bounding box 46.

Alternatively, as shown in FIG. 3C, in many situations, platen surface14 a may include a combination of hills 48 and valleys 50 that occur dueto platen surface 14 a being non-flat (e.g., due to manufacturinglimitations) as well due to surface sloping (e.g., due to installationlimitations). As discussed below, the planarizing process of the presentdisclosure is configured to provide a planar surface relative to the x-ybuild plane regardless of the reasons for non-planarity. In other words,the planarizing process of the present disclosure may compensate for avariety of different planarity deviations relative to the x-y buildplane.

In order to planarize surface platen 14 a, controller system 44 maygenerate and print planarizing part 34 in a manner that effectivelyreduces hills 48 and valleys 50 as shown in FIGS. 3A-3C. For example, asshown in FIGS. 4A-4C, which correspond to the views in FIGS. 3A-3C,controller system 44 may generate planarizing part 34 having a number oflayers 34 t that are preferably sufficient to fill in valleys 50, andmore preferably, sufficient to cover hills 48 by at least one layerthickness.

As can be seen in FIGS. 4A-4C, this provides a top surface 34 t that issubstantially planar relative to the x-y build plane, where top surface34 t may receive subsequently-printed layers of 3D part 30 and supportstructure 32. Additionally, the filling of valleys 50 and covering ofhills 48 define bottom surface 34 b of planarizing part 34, whichsubstantially mirrors the topography of the planarity deviations (i.e.,the topography of hills 48 and valleys 50). This allows planarizingsubstrate 34 to maintain a good adhesive bond to platen surface 14 a,preferably at substantially all locations within bounding box 46.

FIG. 5 is a flow diagram of method 54, which is an example method forprinting 3D parts with an additive manufacturing system using theplanarizing process of the present disclosure. The following discussionof method 54 is made with reference to system 10 (shown in FIG. 1) withthe understanding that method 54 may be performed with any suitableadditive manufacturing system, and is particularly useful for thosesystems having large platens.

As shown, method 54 includes steps 56-74, and is preferably performedfor each printing operation. Nonetheless, in some embodiments, one ormore steps of method 54 may alternatively (or additionally) be performedduring one or more calibration routines that are independent of printingoperations, such as when a platen 14 and/or print head 18 are installedto system 10, during periodic intervals (e.g., daily or weekly), and thelike, and may be performed in any suitable order.

When performed for a printing operation, method 54 involves receiving adigital model of 3D part 30, which is preferably stored on one or morecomputer storage media of controller system 44 (e.g., on computer 40)(step 56). Controller system 44 may also direct system 10 to warm upchamber 12 (or to directly warm up platen 14) to one or more operatingtemperatures for printing 3D part 30 and support structure 32 (step 58).This allows platen 14 to warm up to an equilibrium temperature forsubsequent measurements. Alternatively, in embodiments in which chamber12 is omitted, step 58 may also be omitted.

Controller system 44 may direct print head 18 or other suitablecalibration device to measure the height of platen surface 14 a alongthe z-axis at multiple points across platen surface 14 a (step 60). Insome embodiments, print head 18 may be used to measure the surfaceheights of the multiple points, such as discussed in Leavitt et al.,U.S. patent application Ser. No. 13/422,343. Alternatively, themeasurements may be performed with a separate calibration device, suchas those disclosed in Calderon et al., U.S. Pat. No. 6,629,011; and Dunnet al., U.S. Pat. No. 7,680,555. In further alternative embodiments,system 10 may include one or more non-contact sensors, such as one ormore optical sensors to measure the surface heights of the multiplepoints. The measured height values may then be recorded by controllersystem 44 (i.e., stored one or more computer storage media).

In some embodiments of system 10, as discussed in Skubic et al., U.S.Pat. No. 8,153,183, due to its size, head gantry 20 may bow down at itsmidpoint, causing print head 18 and/or other calibration devicesupported by head gantry 20 to follow this bowed trajectory when movingin the x-y plane. This bowed trajectory may affect the measurements madeduring step 60 of method 54, and can be compensated for by othertechniques, such as those disclosed in Skubic et al., U.S. Pat. No.8,153,183. As such, as used herein the term “substantially planar in thebuild plane”, with reference to top surface 34 t of planarizing part 34,includes deviations from exact flatness due to variations in themovement trajectories of print head 18 and/or calibration device.

In some embodiments, the measurements are made across the entire usablesurface area of platen surface 14 a, such as based an entire usablebuild volume for chamber 12. Alternatively, the measurements are limitedto one or more subregions, such as within a bounding box of 3D part 30and support structure 32 (e.g., bounding box 46). In either case, thesemeasurements provide a mapped topography of platen surface 14 a, whichmay identify any existing hills (e.g., hills 48) and valleys (e.g.,valleys 50) in platen surface 14 a, such as due to manufacturing andinstallation limitations.

The measurements of platen surface 14 a are preferably made withsuitable accuracies relative to the slice thickness of planarizing part34, such as with accuracies within one-half of the smallest slicethickness H_(s) for printing planarizing part 34. For example, forextrusion-based additive manufacturing systems, the slice thicknessesH_(s) may correspond to the smallest expected road heights of thedeposited roads of the part or support materials for printingplanarizing part 34. Alternatively, for jetting-based additivemanufacturing systems, the slice thicknesses H_(s) may corresponded tothe smallest expected deposited jetted droplet sizes for the part orsupport materials for printing planarizing part 34.

In some preferred embodiments, the slice thickness H_(s) for printingplanarizing part 34 is different (e.g., thicker) than the slicethickness used to print 3D part 30 and support structure 32. Forexample, it may be desired that 3D part 30 have a higher resolution, andthus finer slices, than the planarizing part 34. In additionalembodiments, planarizing part 34 itself may be printed with differentslice thicknesses H_(s).

Controller system 44 may then use these measurements to define topsurface 34 t and bottom surface 34 b of the digital model forplanarizing part 34. For instance, controller system 44 may calculate aminimum height for planarizing part 34 that is required to provide asubstantially-planar top surface (e.g., top surface 34 t) based on themeasurements from step 60 (step 62). In a preferred embodiment,controller system 44 initially identifies the highest point of themeasured heights, such as height 48 h of hill 48, and sets this at thepeak height Z_(peak)(x,y).

From there, controller system 44 may then determine the height of topsurface 34 t of planarizing part 34 relative to platen surface 14 a,referred to as height H_(PP), as a function of the peak heightZ_(peak)(x,y) and the slice thickness H_(s) for planarizing part 34. Ina preferred embodiment, controller system 44 may determine the heightH_(PP) of top surface 34 t relative to relative to platen surface 14 aby the following Equation 1:

$H_{PP} = {{Z_{peak}\left( {x,y} \right)} + {\sum\limits_{1}^{n}\;{A_{i}*H_{s,i}}}}$where “n” is the total number of different-sized slices used to createplanarizing part 34, “A” is an integer designating a desired number oflayers for a given slice i, and H_(s,i) is the slice thickness for thegiven slice i, where i ranges from 1 to n. The number n may be a valueof five or less, more preferably four or less, and even more preferablytwo or less.

For example, if planarizing part 34 is generated with a single slicethickness H_(s) (at least for layers above the peak heightZ_(peak)(x,y)) Equation 1 collapses down to the following Equation 2:H _(PP) =Z _(peak)(x,y)+A*H _(s)

In other words, the height H_(PP) of planarizing part 34 relative toplaten surface 14 a is the peak height Z_(peak)(x,y) (e.g., height 48 hof hill 48) plus “A” additional slice thicknesses. The integer “A” ispreferably a low number to reduce printing time and material costs, suchas from one to ten, more preferably from one to five, and mostpreferably one (i.e., a single layer). In this most preferredembodiment, the value n in Equation 1 will also be one. Thismost-preferred embodiment is illustrated above in FIGS. 4A-4C, where thetop-most layer of planaring part 34 having top surface 34 t is one sliceor layer thickness above the peak of hill 48.

As can be appreciated, the above-discussed calculations by computersystem 44 rely on the highest point of the measured heights (e.g.,height 48 h of hill 48) as a reference height. However, in alternativeembodiments, computer system 44 may use other heights as the referenceheight.

For example, in some embodiments, controller system 44 may calculateaverage surface height 52 from the previous measurements, and use thisvalue as the reference height. In these embodiments, controller system44 may then calculate the local height deviations above and below thisreference height (e.g., height deviations 48 d and 50 d) to determinethe height of height H_(PP) of top surface 34 t relative to relative toplaten surface 14 a for a given point of platen surface 14 a in the x-yplane. For example, controller system 44 may determine the height H_(PP)of planarizing part 34 by the following Equation 3:

$H_{PP} = {{Z_{ave}\left( {x,y} \right)} + {Z_{{dev},{ave}}\left( {x,y} \right)} + {\sum\limits_{1}^{n}\;{A_{i}*H_{s,i}}}}$where Z_(ave)(x,y) is the average surface height (e.g., average surfaceheight 52), and Z_(dev,ave)(x,y) is the height deviation between theaverage surface height and the highest point of the measured heights(e.g., height deviation 48 d).

In other embodiments, controller system 44 may use the lowest point ofthe measured heights, such as height 50 h of valley 50, and use thisvalue as the reference height. For example, controller system 44 maydetermine the height H_(PP) of planarizing part 34 by the followingEquation 4:

$H_{PP} = {{Z_{floor}\left( {x,y} \right)} + {Z_{{dev},{floor}}\left( {x,y} \right)} + {\sum\limits_{1}^{n}\;{A_{i}*H_{s,i}}}}$where Z_(floor)(x,y) is the lowest height (e.g., height 50 h), andZ_(dev,floor)(x,y) is the height deviation between the lowest point andthe highest point of the measured heights (e.g., the sum of heightdeviations 48 d and 50 d). In further alternative embodiments, any othersuitable reference height may be used. A comparison of Equations 1-4show their similarities based on where the reference height is set.

Controller system 44 may then generate a digital model of planarizingpart 34 (step 64). For example, the generated digital model ofplanarizing part 34 may include top surface 34 t at height H_(PP), abottom surface 34 b that substantially mirrors the topography of platensurface 14 a, and a perimeter that is preferably defined by bounding box46. Thus, the volume of the generated digital model of planarizing part34 has cross-sectional dimensions in the x-y build plane that arepreferably defined by bounding box 46, an upper limit defined by thesubstantially-planar top surface 34 t, and a lower limit defined by thetopography of bottom surface 34 b.

Controller system 44 may then position (and optionally orient) thedigital model of 3D part 30 at a suitable location above the digitalmodel of planarizing part 34 (step 66). Utilizing a pre-processingprogram, controller system 44 may then slice the digital models of 3Dpart 30 and planarizing part 34 (step 68). Examples of suitablepre-processing programs includes those developed by Stratasys, Inc.,Eden Prairie, Minn. under the trademarks “INSIGHT” and “CATALYST”, whichmay be modified to slice and generate tool path instructions for eachlayer of planarizing part 34.

In some embodiments, the slicing operations for the digital models of 3Dpart 30 and planarizing part 34 may be performed in the same operation,such as with the same layer thicknesses. However, as mentioned above, insome preferred embodiments, planarizing part 34 may have different layerthicknesses than 3D part 30. As such, in these embodiments, the slicingoperations may be performed successively or simultaneously, using thedifferent slice thicknesses.

Because the topography of platen surface 14 a may vary, and because topsurface 34 t at height H_(PP) is substantially planar in the x-y plane,the thickness of planarizing part 34 along the z-axis will vary with thetopography of platen surface 14 a. As such, the number of sliced layersfor planarizing part 34 may also vary with the topography of platensurface 14 a, as illustrated above in FIGS. 4A-4C.

Accordingly, for a given point on platen surface 14 a in the x-y plane,the number of layers for planarizing part 34 may be determined as afunction of the height H_(PP) of top surface 34 t, the height for thegiven point, and the slice thickness H_(s) for printing planarizing part34. In preferred embodiments, for a given point of platen surface 14 ain the x-y plane, the number of layers correspond to the number oflayers extending from platen surface 14 a to top surface 34 ofplanarizing part 34 t (e.g., a single layer above the peak of hill 48).

For instance, for a point taken at the floor of valley 50, the number oflayers equals the difference between the height H_(PP) of top surface 34t (i.e., one slice thickness H_(s) above height 48 h) and height 50 h ofthe floor of valley 50, divided by the slice thickness H_(s). Thiscorresponds to the sum of height deviations 48 d and 50 d, divided bythe slice thickness Hs.

Controller system 44 may then use the pre-processing program to generatelayers for (optional) support structure 32 (step 70), create perimetergeometries for each sliced layer, generate tool path instructions(and/or any other printing information) for 3D part 30, supportstructure 32, and planarizing part 34 (step 72), and transmit theinformation to system 10.

In an alternative embodiment, one or more of the steps for generating adigital model of planarizing part 34, slicing the digital model ofplanarizing part 34, and generating tool path instructions forplanarizing part 34 may be post-processed into the previously-generatedtool path instructions of 3D part 30 and support structure 32 with aseparate post-processing program (after running the pre-processingprogram). This post-processing program may operated manually by a user,or may be invoked in an automated manner by the pre-processing programof controller system 44.

Accordingly, the digital model for planarizing part 34 may be generatedin any desired format. For instance, in some embodiments, controllersystem 44 may generate the digital model of planarizing part 34 in thesame or similar format as the digital model of 3D part 30 (e.g., in anSTL file format). In these embodiments, controller system 44 may thenslice the digital model of planarizing part 34, create perimetergeometries for each sliced layer, and generate tool path instructions,as discussed above for steps 68 and 72 of method 54.

Alternatively, controller system 44 may generate the digital model ofplanarizing part 34 as a pre-sliced set of layer perimeters. In theseembodiments, controller system 44 may then generate tool pathinstructions, as discussed above for step 72 of method 54. In yet afurther alternative embodiment, controller system 44 may generate thedigital model of planarizing part 34 as the tool path instructions.

Upon receipt of the printing instructions, system 10 may then printplanarizing part 34, support structure 32, and 3D part 30 onto platensurface 14 a based on the received printing instructions (e.g., the toolpaths and/or any other printing instructions) (step 74). For example, asshown in FIG. 6, system 10 may print planarizing part 34 to effectivelyflatten the planarity deviations of platen surface 14 a within boundingbox 46. This produces a substantially-planar top surface 34 t to receivethe subsequently printed layers of 3D part 30 and support structure 34.Furthermore, because bottom surface 34 b of planarizing part 34substantially mirrors the topography of platen surface 14 a withinbounding box 46, the printed material of planarizing part 34 achievesgood adhesive bonding to platen surface 14 a at substantially alllocations within bounding box 46.

As shown in FIG. 7, one or more layers of support structure 32 may beprinted on top surface 34 t, and 3D part 30 may then be printed onsupport structure 32. The substantially-planar top surface 34 t ofplanarizing part 34 accordingly allows 3D part 30 and support structure32 to be printed with increased resolutions, while also allowing platen14 to be manufactured and installed with reasonable tolerances.

In the shown embodiment, 3D part 30 and planarizing part 34 may each beprinted from one or more part materials (e.g., the same part material),where support structure 32 resides between them. In this embodiment,support structure 32 may be printed from a support material that isremovable from 3D part 30, such as a soluble support material that maydissolve in an aqueous liquid or solution. Alternatively, supportstructure 32 may be printed from the part material or any other suitablematerial in a configuration designed to allow breaking it away from the3D part 30.

In an alternative embodiment, planarizing part 34 may be printed fromone or more support materials. In this embodiment, 3D part 30 may beprinted directly onto top surface 34 t of planarizing part 34, ratherthan requiring one or more separate layers of support structure 32 toreside therebetween. In further embodiments, planarizing part 34 may beprinted at least in part by a support material and at least in part by apart material (e.g., a combination of part and support materials).

Suitable consumable materials for 3D part 30, support structure 32, andplanarizing part 34 include those disclosed and listed in Crump et al.,U.S. Pat. No. 5,503,785; Lombardi et al., U.S. Pat. Nos. 6,070,107 and6,228,923; Priedeman et al., U.S. Pat. No. 6,790,403; Comb et al., U.S.Pat. No. 7,122,246; Batchelder, U.S. Patent Application Publication No.2009/0263582; Hopkins et al., U.S. Patent Application Publication No.2010/0096072; Batchelder et al., U.S. Patent Application Publication No.2011/0076496; and Batchelder et al., U.S. Patent Application PublicationNo. 2011/0076495.

After the printing operation is completed, the resulting printed object35 may be removed from system 10, and 3D part 30 may be removed fromsupport structure 32 and planarizing part 34. For example, planarizingpart 34 may be broken or cut away from platen 34, and the resultingprinted object 35 may be placed in an aqueous liquid or solution todissolve the soluble support material of support structure 32. Theresulting 3D part 30 may then be removed from the aqueous liquid orsolution for subsequent post-processing, if desired. The dissolvedsupport structure 32 and the planarizing part 34 may also be collectedfrom the aqueous liquid or solution and recycled or otherwise discardedin an environmentally-friendly manner.

Although the present disclosure has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the disclosure.

The invention claimed is:
 1. A method for printing a three-dimensionalpart with an additive manufacturing system having a platen with a platensurface, the method comprising: measuring heights of multiple points ofthe platen surface, wherein the measured heights provide a mappedtopography of the platen surface; calculating a height of a planarizingpart as a function of the measured heights; generating a digital modelof the planarizing part based on the calculated height and the mappedtopography of the platen surface; slicing the digital model of theplanarizing part into multiple layers; printing the planarizing partwith the additive manufacturing system in a layer by layer manner basedon the sliced generated digital model of the planarizing part, theprinted planarizing part including a printed layer forming asubstantially-planar top surface in a build plane, and one or moreprinted layers forming a bottom surface that contacts the platen surfaceand substantially mirrors the mapped topography of the platen surface,wherein the bottom surface of the printed planarization part isnon-parallel to the top surface of the printed planarizing part; andprinting the three-dimensional part on the substantially-planar topsurface of the printed planarizing part.
 2. The method of claim 1,wherein the multiple points of the platen surface are located within abounding box of the three-dimensional part.
 3. The method of claim 1,and further comprising heating at least the platen to one or moreoperating temperatures prior to measuring the heights.
 4. The method ofclaim 1, wherein calculating the height of the planarizing part as afunction of the measured heights comprises: determining a peak height ofthe measured heights; and calculating the height of the planarizing partas a function of the determined peak height and at least one slicethickness for the planarizing part.
 5. The method of claim 4, whereincalculating the height of the planarizing part comprises an equation asfollows:$H_{PP} = {{Z_{peak}\left( {x,y} \right)} + {\sum\limits_{1}^{n}\;{A_{i}*H_{s,i}}}}$wherein n is a total number of different-sized slices for theplanarizing part, A is an integer designating a desired number of layersfor a given slice i, and H_(s,i) is the slice thickness for the givenslice i, and wherein i ranges from 1 to n.
 6. The method of claim 5,wherein the preselected integer A is one, and wherein n is one.
 7. Themethod of claim 1, wherein measuring the heights of the multiple pointsof the platen surface is performed after receiving a digital model ofthe three-dimensional part, and prior to printing the three-dimensionalpart.
 8. The method of claim 1, and further comprising printing asupport structure for the three-dimensional onto thesubstantially-planar top surface of the printed planarizing part,wherein the three-dimensional part is at least partially printed ontothe support structure.
 9. A method for printing a three-dimensional partwith an additive manufacturing system having a platen with a platensurface, the method comprising: measuring heights of multiple points ofthe platen surface, wherein the measured heights provide a mappedtopography of the platen surface; determining a peak height based on themeasured heights; calculating a height for a planarizing part as afunction of the determined peak height and at least one slice thicknessfor the planarizing part; generating a digital model of the planarizingpart having a substantially-planar top surface at the calculated height,and a bottom surface that mirrors the mapped topography of the platensurface; slicing the digital model of the planarizing part into multiplelayers; and printing the planarizing part in a layer by layer mannerwith the additive manufacturing system based on the generated and sliceddigital model of the planarizing part, the printed planarizing partincluding a substantially-planar top surface in a build plane, and abottom surface that contacts the platen surface and substantiallymirrors the mapped topography of the platen surface, wherein the bottomsurface of the printed planarization part is non-parallel to the topsurface of the printed planarizing part.
 10. The method of claim 9, andfurther comprising printing at least one of the three-dimensional partand a support structure for the three-dimensional part onto the printedplanarizing part.
 11. The method of claim 9, wherein the multiple pointsof the platen surface are located within a bounding box of at least oneof the three-dimensional part and the support structure.
 12. The methodof claim 9, and further comprising slicing the digital model of theplanarizing part into a number of layers, wherein the number of layersvaries with the mapped topography of the platen surface.
 13. The methodof claim 9, wherein calculating the height of the planarizing partcomprises an equation as follows:$H_{PP} = {{Z_{peak}\left( {x,y} \right)} + {\sum\limits_{1}^{n}\;{A_{i}*H_{s,i}}}}$wherein n is a total number of different-sized slices for theplanarizing part, A is an integer designating a desired number of layersfor a given slice i, and H_(s,i) is the slice thickness for the givenslice i, and wherein i ranges from 1 to n.
 14. An object printed with anadditive manufacturing system having a platen with a platen surface, theobject comprising: a three-dimensional part; optionally, a supportstructure for the three-dimensional part, wherein the three-dimensionalpart and the optional support structure have a bounding box in a buildplane; and a planarizing part comprising: a top surface on which one orboth of the three-dimensional part and the optional support structureare printed, wherein the top surface is formed by a printed layer and issubstantially planar in the build plane; a bottom surface that contactsthe platen surface and substantially mirrors a topography of the platensurface, wherein the bottom surface is formed of one or more printedlayers and is non-parallel to the top surface of the planarizing part;and a cross-section in the build plane defined at least in part by thebounding box.
 15. The object of claim 14, wherein the planarizing partis formed of a plurality of printed layers, each printed layer having alayer thickness, and the top surface of the planarizing part has aheight that is at least one layer thickness greater than a peak heightof the platen surface within the bounding box.
 16. The object of claim15, wherein the at least one layer thickness is one layer thickness. 17.The object of claim 14, wherein the three-dimensional part and theplanarizing part are printed with different layer thicknesses.
 18. Theobject of claim 14, wherein the planarizing part and thethree-dimensional part are printed from the same part material.
 19. Theobject of claim 14, wherein at least a portion of the planarizing partis printed from a soluble support material.